'\" te
.\" Copyright (c) 2006, Sun Microsystems, Inc. All Rights Reserved.
.\" Copyright 1989 AT&T
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
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.TH GETQ 9F "Jan 16, 2006"
.SH NAME
getq \- get the next message from a queue
.SH SYNOPSIS
.LP
.nf
#include <sys/stream.h>



\fBmblk_t *\fR\fBgetq\fR(\fBqueue_t *\fR\fIq\fR);
.fi

.SH INTERFACE LEVEL
.sp
.LP
Architecture independent level 1 (DDI/DKI).
.SH PARAMETERS
.sp
.ne 2
.na
\fB\fIq\fR\fR
.ad
.RS 5n
Pointer to the queue from which the message is to be retrieved.
.RE

.SH DESCRIPTION
.sp
.LP
The \fBgetq()\fR function is used by a service ( \fBsrv\fR(9E)) routine to
retrieve its enqueued messages.
.sp
.LP
A module or driver may include a service routine to process enqueued messages.
Once the \fBSTREAMS \fRscheduler calls \fBsrv()\fR it must process all enqueued
messages, unless prevented by flow control. \fBgetq()\fR obtains the next
available message from the top of the queue pointed to by \fIq\fR. It should be
called in a \fBwhile\fR loop that is exited only when there are no more
messages or flow control prevents further processing.
.sp
.LP
If an attempt was made to write to the queue while it was blocked by flow
control, \fBgetq()\fR back-enables (restarts) the service routine once it falls
below the low water mark.
.SH RETURN VALUES
.sp
.LP
If there is a message to retrieve, \fBgetq()\fR returns a pointer to it. If no
message is queued, \fBgetq()\fR returns a \fBNULL\fR pointer.
.SH CONTEXT
.sp
.LP
The \fBgetq()\fR function can be called from user, interrupt, or kernel
context.
.SH EXAMPLES
.sp
.LP
See \fBdupb\fR(9F).
.SH SEE ALSO
.sp
.LP
.BR srv (9E),
.BR bcanput (9F),
.BR canput (9F),
.BR dupb (9F),
.BR putbq (9F),
.BR putq (9F),
.BR qenable (9F)
.sp
.LP
\fIWriting Device Drivers\fR
.sp
.LP
\fISTREAMS Programming Guide\fR
